A recent study published in Science (October 2011) indicates a new discovery has been made as to how the brain connects to form memories of events that happen close together, and could play a major role in furthering research on Alzheimer’s disease and other forms of dementia.
Researchers from the Massachusetts Institute of Technology, led by Dr. Junghyup Suh, found the link between the hippocampus and the entorhinal cortex (EC). The entorhinal cortex is located near the medial temporal lobe of the brain and functions as the central port for navigating memory (the hub) from all areas of the brain back to the hippocampus. It is the main terminal between the hippocampus and the neocortex, which is involved in higher functioning for conscious thought, language, motor skills, sensory perception, and spatial reasoning.
The EC plays an important role in several different types of memories: autobiographical, declarative, episodic memories and in particular spatial memories. It is instrumental in the formation and consolidating of memory, and the optimization of memory during sleep. The EC is also responsible for the association of impulse signals between the eyes and the ears.
Researchers tested their theory by a mutant strain of specifically bred mice. They were able to disable the cells in the entorhinal cortex of the mice brains by taking doxycycline from their food.
When the control mice (normal) were given a shock 20 seconds after they heard a sound they learned to associate the sound with the shock. Soon they froze in their tracks as soon as they heard the noise. The mutant mice, however, were less likely to react to the sound. When the shock was given at the same time as the sound, there was no difference in reaction between the normal mice and the mutant mice. This indicated to the researchers there is a connection between time and the entorhinal cortex.
In another experiment, mice were placed on a small platform and after 30 seconds were put into a water maze. Normal mice would return to the platform to rest after swimming the maze. The mutant mice has a difficult time finding their way back to the platform after they were placed in the water maze, even though only a few seconds had elapsed. Associating and short-term memory between what was currently happening seemed to be more difficult for the mutant mice.
So you thought you were the only one having challenges improving memory, mice are having problems too!
This is Ron White, two-time USA Memory Champion , memory training expert, and memory keynote speaker. Patients with Alzheimer’s disease have difficulty with memory. According to research, the entorhinal cortex is one of the first areas of the brain damaged in the disease. This research indicates that the entorhinal cortex and its communication to the hippocampus are critical in the formation and retention of memory.
Sources:
Medical Press – Brain circuits connected with memory discovered: http://medicalxpress.com/news/2011-11-brain-circuits-memory.html
Wikipedia – Entorhinal cortex: http://en.wikipedia.org/wiki/Entorhinal_cortex